One level of transcriptional control appears to reside in the protein content and conformation of nucleosomes comprising active gene sequences. If gene regulation proteins are bound nonrandomly over the genome, then the segregation of preexisting molecules and the deposition of nascent molecules should also be nonradom during the replication of chromatin. Using a combination of density labeling, protein crosslinking, ultracentrifugation and gel electrophoresis, we propose to study the deposition and segregation of the HMG proteins, histone Hl and semihistone A24. Further experiments will attempt to isolate and characterize the Hl-core histone, histone-HMG and HMG-HMG crosslinked protein complexes.